- Modified Type 1F Unbound Mixtures must be made from natural aggregate (excluding uncrushed flint based or quartz based gravels), recycled aggregates, manufactured aggregates or well burnt non-plastic shale, or a combination of these, and may contain up to 10% by mass of natural sand passing a 4 mm test sieve.
- The mixture must comply with BS EN 13285 and the grading requirements of Table A10.1.
Table A10.1 Grading for Modified Type 1F Unbound Mixture (0/20) Sieve size, mm Percentage by mass passing Overall grading range Supplier declared value grading range Tolerance on the supplier declared value 40 100 --- --- 20 75 - 99 --- --- 10 43 - 81 54 - 72 ± 15 4 23 - 66 33 - 52 ± 15 2 12 - 53 21 - 38 ± 15 1 6 - 42 14 - 27 ± 13 0.5 3 - 32 9 - 20 ± 10 0.063 0 - 12 --- --- Grading of individual batches – differences passing selected sieves Retained sieve size, mm Passing sieve size, mm Percentage by mass passing Not less than Not more than 4 10 7 30 2 4 7 30
- Aggregates used in the mixture must be in accordance with BS EN 13242 and Table A10.2.
Table A10.2 Requirements for aggregates used in Modified Type 1F Unbound Mixture Crushed, or broken and totally rounded particles crushed rock, crushed manufactured and crushed recycled aggregates (see NOTE) C90/3 Resistance to fragmentation – Los Angeles test LA50 Resistance to wear – micro-Deval test MDE NR (no requirement). The supplier must state the value for the aggregate used Resistance to freezing and thawing – magnesium sulphate soundness MS35 Water absorption WA24NR (no requirement). The supplier must state the value for the aggregate used. Volume stability of blast furnace slags Free from dicalcium silicate and iron disintegration Volume stability of steel (BOF and EAF) slags V5 All other BS EN 13242 aggregate requirements Category NR (no requirement). Note: BS EN 13242 assumes that crushed rock aggregates comply with category C90/3 without further testing.
- The size fraction of the unbound mixture passing a 0.425 mm size test sieve must be non-plastic, as defined by BS EN 17892-12:2018, and tested in compliance therewith.
- Where the mixture contains recycled coarse aggregate or recycled concrete aggregate, it must be classified by hand sorting the coarse aggregate particles in accordance with BS EN 933-11. The test must be carried out by a suitably trained laboratory technician competent in classifying the constituent classes in accordance with the test method. Recycled coarse aggregate and recycled concrete aggregate must also comply with the requirements of Table A10.3.
Table A10.3. Recycled coarse aggregate and recycled concrete aggregate used in Modified Type 1F Unbound Mixtures Component Maximum permitted
content (% by mass)
Asphalt (Class Ra) 50 Glass (Class Rg) 25 Other materials (Class X), including wood, plastic and metal 1
- The Modified Type 1F Unbound Mixtures must be non-frost susceptible. Material is classed as non-frost-susceptible if the mean heave is 15 mm or less when tested in accordance with BS 812-124. Comparator specimens with Annex B of BS 812-124 must be used.